We observed the methane flux of 12 experimental plots near Toolik Lake, Alaska. Plot location was chosen based on dominate vegetation type (T or W). The tussock tundra plots are located near the Moist Acidic Tundra plots characterized by Shaver ad Chapin (1991). The wet sedge plots are located near the outlet of Toolik Lake; all plots have been used by the Arctic LTER project at Toolik Lake.

In wet sedge tundra, three 1 m2-sized plots were positioned randomly in each of two treatments of block 2 of the LTER wet sedge scheme (outlet site), control and N+P-fertilized , respectively, in 2000. Paired control and fertilized plots were labelled with 14C and 15N at one of three different dates of the summer season 2001.

In moist acidic tussock tundra six 1 m2 sized plots were positioned in three of the "X" (=extra") blocks of the LTER scheme, in 2001, inside an area extending 5 m from the boardwalks and, positioning plots so that similar area shares between tussocks and intertussock areas was achieved. In each of the three X blocks two 1m2-sized plots were established. The whole 5 m area of the X blocks extending from the board walks was divided into two halfs, each containing one of the 1m2 sized plots. One half was set aside as the control and the other half was designated to be fertilized. Fertilization with a Hoagland solution (see protocol) started in late summer 2001, and was repeated annually after that , early in the summer season. Paired control and fertilized plots were labelled with 14C and 15N of the summer season 2002; all three pairs were labelled as closely together in time as logistically possible.

Sampling description:
We used the static chamber method for each sampling event, covering the plot with a plexiglass fluxing chamber and a shade cloth to maintain a cool temperature. At twenty minute intervals for a total of 60 minutes, we obtained 10-20 mL of chamber air in nylong, airtight syringes. The syringes were returned to the laboratory at the Toolik Field Station and were ran on a Shimadzu model 14A gas chromatograph with a flame ionization detector (FID). The chromatograph peak areas were converted to concentration based on a standard curve.

Methane fluxes were calculated using a linear regression of the syringe concentrations that characterized the change in methane concentration in the flux chamber over time.

Shaver, G.R., and F.S. Chapin. 1991. Production - biomass relationships and elemental cycling in contrasting arctic vegetation types. Ecological Monographs 61(1): 1-31.